1. Field of the Invention
The present invention relates to a suction valve including a valve seat and a valve guard between which a valve element is arranged in a reciprocating manner, and further including an unloader having a plurality of unloader fingers which reach through passage channels in the valve seat and rest against the valve element, whereby the unloader is arranged in a rotationally locked manner with respect to the valve seat and is guided in the axial direction by means of an anti-rotation lock.
2. The Prior Art
Suction valves of compressors are often designed with unloaders. As it is well known, unloaders serve substantially to start up the compressor under no load, or to switch the compressor to an idling operation, or to control the compressor.
In order to prevent wear on the guides of the unloader, especially in case of dry-running compressors, guide strips and guide rings have been used for years in the unloader guides as shown, e.g., in EP 686 770 A2 or DE 44 31 512 A1. In addition, rotation of the unloader can be limited by using stopping blocks made of plastic. Said stopping blocks are screwed by means of screws to the valve seat, preferably radially on the inside between two adjacent unloader fingers. If an anti-rotation lock would be omitted, the unloader fingers, due to the rotation of the unloader, would rub against the webs of the through-openings at the valve seat and could cause damage to the valve and/or unloader itself due to the resulting high degree of wear. However, due to the variety of geometries of valve designs, said stopping blocks have to be custom-made for each valve, which is costly, and have to be provided and stored in small numbers. Costs caused in this manner are correspondingly high. Moreover, the stopping blocks, in particular in case of small valves, can negatively influence the flow conditions in the valve.
From EP 1 936 194 A1 (see U.S. Patent Application Publication 2008149195) an anti-rotation lock for an unloader is already known which resolves the above-mentioned disadvantages. Here, an anti-rotation locking sleeve is provided which has a non-circular cross-section which is arranged non-rotatably and concentrically on the valve seat and on which the unloader is arranged with a correspondingly shaped, diametrically opposed central section. Due to the non-circular cross-section of the anti-rotation locking sleeve, a rotation of the unloader relative to the valve seat is prevented. The anti-rotation locking sleeve assumes at the same time the guiding function of the unloader. However, the anti-rotation lock has the disadvantage that, on the one hand, the axial length of the valve is enlarged by the anti-rotation locking sleeve, which makes the use impossible, in particular in case of controlled valves or unloaders. Also, the enlarged overall length usually makes it impossible to retrofit existing valves. If retrofitting is possible due to the available installation space, it is necessary, however, to replace the entire unloader and additionally to rework the valve seat, which makes retrofitting unfeasible in many cases from a practical point of view. On the other hand, a secure and durable function of the anti-rotation lock for the unloader requires machining the valve seat, which increases the production costs for such a valve.
It is therefore the object of the present invention to provide an anti-rotation lock for an unloader of a suction valve which is compact, is constructed and manufactured in a simple manner, and allows retrofitting of existing valves in a simple manner.